Vestaron makes an eco-friendly pesticide derived from spider venom. Bagaveev uses 3-D printers to make rocket engines for nanosatellites. Transatomic Power is developing a next-generation reactor that runs on nuclear waste.

They all have one thing in common: money from Silicon Valley venture capitalists.

After years of shying away from science, engineering and clean-technology start-ups, investors are beginning to take an interest in them again, raising hopes among entrepreneurs in those areas that a long slump is finally over. But these start-ups face intense pressure to prove that their science can turn a profit more quickly than hot tech companies like Snapchat and Uber.

In August, the Founders Fund, which has backed social networks like Facebook and Yammer and the streaming-music service Spotify, announced a $2 million investment in Transatomic Power of Cambridge, Mass. Days earlier, Y Combinator, known for aiding web and mobile-app start-ups like the social news site Reddit and the game maker Omgpop, took part in a $1.5 million early investment in Helion Energy, which is developing an engine powered by nuclear fusion.

Click here to read more from this October 12, 2014 New York Times article by Hiroko Tabuchi.